This invention relates to a method of reinforcing porous materials.
Porous materials including inorganic fiber boards such as rock wool boards and asbestos boards and organic fiber boards such as insulation boards are lightweight and convenient to handle because of low specific gravity, inexpensive to manufacture and excellent in heat insulating properties and soundproofing properties. Although suitable for use as construction materials in these respects, they have yet to be improved in strength. Accordingly attempts have heretofore been made to impart increased strength to such porous materials. In making rock wool fiber boards by a wet method, for example, it is known to admix plaster of Paris with a slurry starting material, but the resulting product, which has increased hardness, is still low in bending strength and internal cohesive force. It has also been attempted to admix corn starch with the slurry starting material. This method fails to give products which are satisfactory in bending strength, internal cohesive force and hardness. Another method is also known in which pulp is admixed with the slurry starting material. Although the method ensures effective entanglement of the fibers, thereby affording somewhat increased bending strength and greater internal cohesive force, the product still remains to be improved.